Sarcina in Sputum Cytology in a Patient of Pulmonary Tuberculosis.

Sir,

Sarcina ventriculi, identified as human pathogen by John Goodsir in 1842, are gram positive strict anaerobic coccus.[1] Although the pathogenicity is still not fully understood, S. ventriculi is associated with delayed gastric emptying, emphysematous gastritis, gastric perforation, and gastric outlet obstruction.[12] S. ventriculi thrives and multiplies in an acidic gastric environment, and carbohydrates and other growth nutrients present in food accumulated in stomach due to gastric stasis.[12] Found ubiquitously in the air and soil, some contends that stomach is its natural habitat as it has been isolated from the feces of healthy humans, mainly those with vegetarian diet.[12] Although well documented in histopathology of gastric diseases, presence of S. ventriculi in respiratory tract is rare and only a few cases have been reported in cytology.[34]

A 52-year-old male patient presented with fever and cough of 1 month duration. He was a chronic smoker with known type 2 diabetes patient on irregular medication. He did not complain of any gastrointestinal symptoms. On respiratory examination, he had reduced intensity of breath sounds with stony dull note over the bilateral lung fields. The palpation of the neck nodes revealed a single level II left cervical lymph node measuring 2 cm in diameter. The laboratory findings showed an elevated erythrocyte sedimentation rate of 85 mm at the end of hour. His blood glucose was 262 mg/dl. Antiretroviral antibody was non-reactive. Chest radiograph revealed bilateral cavitary lesion with patchy consolidation. Sputum examination revealed acid fast bacilli on Ziehl-Neelsen stain [Figure 1]. Thus, confirming the diagnosis of pulmonary tuberculosis. Smears made from sputum also showed cocci arranged in tetrads and octads, which were gram positive. The morphology of these organisms was conforming to that of S. ventriculi [Figure 2]. Periodic acid Schiff stain did not reveal any fungal organisms. The fine needle aspiration of the left cervical lymph node revealed caseating epithelioid cell granulomas. Sputum culture was sent, which showed Mycobacterium tuberculosis on the Löwenstein–Jensen medium. However, routine culture for bacteria and fungus was negative. Blood sugar of the patient was controlled. He was started with rifampicin, isoniazid, pyrazinamide, and ethambutol for the 2 months followed by rifampicin, isoniazid, and pyrazinamide for further 4 months. After 6 months of follow-up, there was resolution of lung lesions.

Figure 1

Sputum smear showing acid fast bacilli (Ziehl Neelsen stain ×1000)

Figure 2

Sputum smear showing Sarcina arranged in tetrads marked by arrow (Haematoxylin and eosin ×1000)

Routine culture may fail to yield S. ventriculi as it is fastidious in nature.[3] The histological appearance of S. ventriculi is unique, and failure to isolate these organisms does not rule out infection.[3] Molecular methods may resolve ambiguity in cases where cultures are negative.[1] Histologically, S. ventriculi is basophilic in hematoxylin and eosin stain with tetrad packet arrangement because of the replication occurring in at least 2 planes of growth.[2] The individual size is 1.8 to 3 μm, or packets of approximate size of a red blood cell.[2] It is refractile in nature, thus can mimic vegetable matter.[2]

In the present case, S. ventriculi were found in the upper respiratory tract in a pulmonary tuberculosis patient, who was known to have type 2 diabetes. Chouguleet al. has reported the presence of S. ventriculi in a case of pulmonary gangrene in a poorly controlled diabetes patient.[3] They explained the colonization and growth of S. ventriculi in the respiratory tract in their patient because of aspiration of gastric contents due to diabetic gastroparesis.[3] Moreover, S. ventriculi species have been isolated in 1.97% of respiratory tract infections.[5] The present case also documents the presence of S. ventriculi in sputum cytology. Bhagat et al. reported a case, where S. ventriculi was diagnosed on fine needle aspiration cytology in a patient of gastric adenocarcinoma.[4]

The differential diagnoses of S. ventriculi are Micrococcus species, Sarcina maxima, and Staphylococcus species on light microscopy.[2] Micrococcus is much smaller than S. ventriculi measuring only 0.5 μm and tends to form clusters as opposed to S. ventriculi.[24] Sarcina maxima lack the thick extracellular layer, which renders S. ventriculi refratile.[2] Staphylococcus is smaller measuring approximately 1 μm in diameter and is arranged in characteristic grapelike clusters, rather than a tetrad pattern.[2]

The presence of S. ventriculi in the sputum suggests respiratory tract infection by this organism, which in this case could be secondary to pulmonary tuberculosis. Second, S. ventriculi in the sputum could be because of the aspiration of gastric contents, which in this case was due to diabetic gastroparesis. Hence, it is important to identify S. ventriculi in the sputum cytology, as the presence of this organism may point toward an underlying lung or gastric pathology.

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