"First Reported Case of Rapidly Progressive Pyogenic Liver Abscess with Isolation of Priestia megaterium: Case Report...

Priestia megaterium (formerly Bacillus megaterium) is a Gram-positive, spore-forming environmental bacillus rarely associated with human infection. In this report, we present a case of a rapidly progressive polymicrobial pyogenic liver abscess with subsequent isolation of P. megaterium in a 69-year-old woman with type II diabetes mellitus, chronic kidney disease, metabolic liver disease, and extensive antibiotic allergies. She initially presented with progressive abdominal pain and fever, with negative early imaging studies. Three weeks later, computed tomography (CT) demonstrated new hepatic abscesses. Interventional radiology drainage cultures initially grew Streptococcus intermedius, guiding targeted antimicrobial therapy; however, the patient clinically deteriorated with recurrent abscess formation despite drainage and broad-spectrum coverage. Subsequent aspirate cultures from the abscess fluid later grew P. megaterium, though this result was finalized after the patient's death on day 12 of admission despite intensive care and source control attempts. This case suggests that P. megaterium, traditionally regarded as nonpathogenic, may be recovered in severe infections in immunocompromised hosts; however, alternative explanations-including polymicrobial infection, antibiotic-mediated suppression of co-pathogens, iatrogenic introduction during drainage procedures, or culture contamination-must be carefully considered. Contributing factors likely included her underlying comorbidities, concurrent COVID-19 infection, delayed pathogen identification, and restrictions imposed by multiple drug allergies. Diagnostic challenges underscore the importance of repeated culture sampling, careful interpretation of microbiology results, and awareness of rare organisms when standard therapy is unsuccessful. This report expands the spectrum of diseases associated with P. megaterium. It emphasizes the need for multidisciplinary collaboration and heightened clinical vigilance in cases of rapidly progressive intra-abdominal infections that are unresponsive to conventional treatment.