Polymicrobial sepsis

Parham Sendi; Peter Graber; Rene Lötscher

doi:10.1503/cmaj.060728

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Figure. Peripheral-blood smears with Giemsa (upper image) and acridin orange staining (lower image) from an 85-year-old woman, 20 days after a surgical repair of a perforated duodenal ulcer. She had recently begun to experience mental confusion, gastrointestinal blood loss and tachycardia.

Our patient was not febrile, which is often the case for septic elderly patients (Am J Med 1996;100:65–70), but blood tests revealed leukocytosis (16.2 × 10⁹/L; normal 4.0–10.0 × 10⁹/L) and an elevated neutrophil cell count (16.0 [normal 2.0–7.0] × 10⁹/L) with a left shift of 68.5% band forms (normal < 10%).

Bacteria are rarely seen in routine blood smears. In her case there were early indications of polymicrobial sepsis in a blood sample taken the day after the onset of her decline. Giemsa staining revealed neutrophils with ingested bacteria (Fig. 1, arrow). Gram staining was inconclusive, but acridin-orange staining showed bacteria with 2 different morphologies: cocci in tetrads (Fig. 2, arrowhead) and rods (arrow). Blood cultures ultimately grew Mitis-group streptococci and Klebsiella pneumoniae. Since K. pneumoniae are nonmotile, rod-shaped bacteria with a prominent polysaccharide capsule, and Streptococcus species are round cocci, these organisms were likely to correspond to those seen in the neutrophils.

Fig. 1: No caption available.

Fig. 2: No caption available.

The source of the organisms was unknown, but endoscopy did reveal small gastric erosions. Despite the administration of proton-pump inhibitors, packed red blood cells, fresh frozen plasma and antibiotics, her condition worsened; she died of septic shock 3 days after her decline.

Granulocytes and macrophages have evolved to ingest as many bacteria as possible and kill them with a combination of various microbicidal sytems. The identification on blood smears of such phagocytes containing bacteria can allow early diagnosis of bacteremia, sometimes while results from blood cultures are still pending. In these very rare cases, ingested bacteria seen in granulocytes in a peripheral-blood smear should lead to early implementation of therapy for sepsis.