A50-34 When Commensals Turn Deadly: Lactobacillus-Induced Septic Shock in a Patient on Total Parenteral Nutrition

Abstract Background Lactobacillus species are gram-positive, facultative anaerobic rods typically regarded as non-pathogenic commensals of the gastrointestinal and genitourinary tracts and are commonly used as probiotics. Despite this benign reputation, Lactobacillus can rarely cause severe infections such as bacteremia, endocarditis, and septic shock, particularly in immunocompromised or critically ill patients. We present a rare case of Lactobacillus rhamnosus-associated septic shock in a patient receiving total parenteral nutrition (TPN). Case Presentation A 55-year-old male with a history of small bowel obstruction requiring prolonged TPN via a peripherally inserted central catheter (PICC) presented to the ICU with fever, hypotension, and altered mental status after four weeks of home TPN. On arrival, he was diaphoretic and confused with cool extremities, blood pressure 82/50 mmHg, heart rate 112 bpm, temperature 38.8 °C, respiratory rate 26 breaths per minute, and oxygen saturation 94% on room air. Laboratory studies revealed leukocytosis (WBC 18,000/mm³), elevated lactate (5.2 mmol/L), acute kidney injury (creatinine 2.1 mg/dL; baseline 1.0 mg/dL), and increased procalcitonin. He received intravenous fluids, vasopressor support with norepinephrine, and empiric broad-spectrum antibiotics (vancomycin plus piperacillin-tazobactam). Blood cultures from both the PICC line and peripheral sites grew Lactobacillus species within 24 hours. The PICC line was removed, and its tip culture also yielded Lactobacillus. The isolate was identified as Lactobacillus rhamnosus via MALDI-TOF mass spectrometry. Transthoracic echocardiography demonstrated no valvular vegetations or evidence of infective endocarditis, excluding an intracardiac source. Susceptibility testing revealed vancomycin resistance but ampicillin and clindamycin sensitivity. Therapy was narrowed to intravenous ampicillin. The patient improved rapidly, with vasopressor discontinuation within 48 hours, and completed a 14-day course of antibiotics with full recovery. Discussion Lactobacillus is a rare but recognized cause of bloodstream infection in patients with disrupted mucosal barriers or central venous access. It is often dismissed as a contaminant, delaying appropriate therapy. Its intrinsic vancomycin resistance complicates empiric management in septic shock. In this case, catheter-related seeding was the likely mechanism of infection. Species identification and susceptibility testing were essential for clinical resolution. Conclusion Clinicians should maintain a high index of suspicion for Lactobacillus as a true pathogen in high-risk patients, especially those on TPN or with indwelling catheters. Early recognition, source control, echocardiographic evaluation to rule out endocarditis, and targeted antimicrobial therapy are critical for survival. This abstract is funded by: None