Case of the Month - January 2022 A 90-year-old woman was brought to the E.R. because of confusion, lethargy, poor appetite, and fever. Her medical history was notable for dementia, hypertension, osteoarthritis, and asthma, but she was usually able to manage most ordinary activities at home, like showering and meals, on her own, but her apartment was a mess and a rodent infestation was reported. Physical exam included initial blood pressure 152/58, pulse 79, respirations 16, and temp 98.4. The remainder of the exam was notable for an elderly dehydrated women with dry mucous membranes, clear lungs, a normal heart exam, no abdominal tenderness, no edema, and no rashes. Her wbc was 18.3K/mm3, hct 35%, plt 572K/mm3, and chemistries inlcuded a creatinine of 0.6 mg/dLand a bicarb of 27 mg/dL. The liver panel was normal except for an albumin of 2.9 g/dL. After 5 days of incubation, an aerobic blood culture bottle obtained in the Emergency Room turned positive. Gram stain revealed filamentous Gram negative rods (Fig. 1). Faint growth of the organism was seen under aerobic conditions on 5% sheep blood agar (Fig. 2) but better growth was observed under anaerobic conditions (Figure. 3). The recovered organism is known to be extremely fastidious, with growth in blood culture bottles inhibited by the presence of SPS in the media. The organism grows optimally under microaerophilic conditions on culture media supplemented with 20% blood, serum, or ascites. This organism is one of the few bacterial species that spontaneously converts to L-forms (cell-wall defective variants). What is the organism? Figure 1 - Gram stain from the blood culture bottle. Figure 2. Aerobic growth on 5% sheep blood agar. Figure 3: Anaerobic growth on CDC-anaerobic plate with 5% sheep blood.