Morganella morganii: an opportunistic multidrug-resistant pathogen isolated in ascitic fluid in an old man, case report and literature review

Abstract

Morganella morganii is commonly found in nature and is also part of the normal intestinal flora in humans and animals. Although typically an opportunistic pathogen, it is rarely isolated in human infections. Infections caused by this bacterium primarily include postoperative wound infections, urinary tract infections, sepsis, abscesses, chorioamnionitis, and cellulitis. The emergence of multidrug-resistant strains poses a significant public health concern, as these strains can lead to severe or even fatal infections in vulnerable patients. We report the case of a 94-year-old immunocompromised patient admitted to the emergency department with dyspnea, significant ascites, and prolonged fever. A C-TAP scan revealed chronic liver disease with large-volume ascites. Laboratory tests showed a mild inflammatory response (CRP: 14 mg/L), low prothrombin time (PT: 56%), hypoalbuminemia (19 g/L), pancytopenia, and macrocytic anemia. Cytobacteriological analysis of the ascitic fluid revealed a significant neutrophilic response and the growth of Morganella morganii. Antibiotic susceptibility testing showed susceptibility to carbapenems, fluoroquinolones, co-trimoxazole, and chloramphenicol, while resistance was observed against penicillins (aminopenicillins, carboxypenicillins, ureidopenicillins), cephalosporins, fosfomycin/trometamol, and aminoglycosides. The multidrug-resistant strain of Morganella morganii in this case demonstrated concerning resistance to most β-lactams, aminoglycosides, and fosfomycin/trometamol. Given its increasingly opportunistic nature, multidrug resistance, and potential to cause severe nosocomial infections, clinicians must consider this bacterium during the diagnostic process.