eng Science and Education Publishing American Journal of Medical Case Reports 2374-216X 2023-03-07 11 3 49 51 10.12691/ajmcr-11-3-2 AJMCR20231132 article Ahmad El-Gammal ahmadelgammal93@gmail.com 1 Ahmad Subahi 1 Hussein Gaith 1 MD Hanady Dass 2 Department of Internal medicine, Beaumont Hospital, Dearborn, MI Division of Infectious Disease, Department of Internal Medicine, Beaumont Hospital, Dearborn, MI Lactobacilli are anaerobic or facultative, Gram-positive bacilli that commonly colonize the gastrointestinal and genitourinary tracts. The most common species of Lactobacillus are Lactobacillus casei and Lactobacillus rhamnosus. Although Lactobacillus species are generally thought to be protective and nonpathogenic microorganisms, they can lead to significant life-threatening infections in immunocompromised patients, labeling them as opportunistic pathogens. We present a case of pathogenic Lactobacilus casei causing an empyema in an immunocompromised patient, which is the first reported case of this nature. http://pubs.sciepub.com/ajmcr/11/3/2/ajmcr-11-3-2.pdf lactobacilus empyema lactobacilus casei