Pasteurella multocida is an opportunistic pathogen and a bacterium that is commonly found in the respiratory and digestive tracts of many animals including poultry (Chen et al., 2002). P. multocida is a small, nonmotile, facultative anaerobic gram-negative coccobacillus, with a length of approximately 1.0–2.0 μm and a width of approximately 0.3–1.0 μm (Peng et al., 2019). The bacterium possesses various potential virulence factors, including a capsule, lipopolysaccharide, sialidase, hyaluronidase, and toxins (Wilkie et al., 2012). P. multocida can infect various hosts, including humans, livestock, and wildlife (Smith et al., 2021). Previous human cases have reported P. multocida causing localized cellulitis, bloodstream infections, meningitis, peritonitis, pneumonia, and endocarditis, with these infections often associated with a history of close contact with animals (Jones and Lockton, 1987; Nettles and Sexton, 1997; Raj et al., 2000; O’Neill et al., 2005; Kofteridis et al., 2009; Rondon-Berrios and Trevejo-Nunez, 2010). However, cases of multi-site infections caused by P. multocida are rare (Fernández-Esparrach et al., 1994; Guilbart et al., 2015; Rueda Prada et al., 2022). Herein, we present a case of multi-site infection involving bloodstream infection, peritonitis, and pneumonia caused by P. multocida. Remarkably, the patient had no history of animal contact, which distinguishes this case from previous case reports. Several previously reported cases of P. multocida-related peritonitis were associated with a history of peritoneal dialysis (Cooke et al., 2004; Rondon-Berrios and Trevejo-Nunez, 2010), whereas the patient we describe did not have underlying kidney disease or a history of peritoneal dialysis. Additionally, previous case reports have suggested that patients with underlying immunodeficiency and liver dysfunction are more susceptible to developing bloodstream infections (Weber et al., 1984; Talley et al., 2016), and these high-risk factors were also present in our patient with bloodstream infection. P. multocida commonly infects the respiratory tract, leading to varying degrees of respiratory infections such as pneumonia, empyema, and lung abscess (Fernández-Esparrach et al., 1994; Lion et al., 1999; Kofteridis et al., 2009), with pneumonia being the predominant manifestation in the reported cases.

P. multocida, a facultative anaerobic gram-negative coccobacillus, is primarily found in the normal oropharyngeal flora of animals. Direct contact with animals or through pet ownership increases the risk of P. multocida infection. Most of the previously reported cases of P. multocida infection have been associated with bites, scratches, or close contact with cats, dogs, and other animals (Talan et al., 1999). However, it is worth noting that humans can become infected with P. multocida even without direct animal contact, by inhaling secretions contaminated with the bacterium, although this mode of transmission is relatively rare (Wilson and Ho, 2013). In the current case, the patient had no history of animal contact but had underlying cirrhosis. This highlights the importance for clinicians to consider the possibility of P. multocida infection, even in the absence of animal exposure, especially when patients have underlying immunodeficiency conditions such as cirrhosis.

Previous reports have primarily focused on P. multocida causing systemic single-organ infections, and only a few cases of simultaneous multi-site infections involving three or more sites in the body have been reported (Fernández-Esparrach et al., 1994; Guilbart et al., 2015; Rueda Prada et al., 2022). Patients with underlying immunodeficiency conditions such as liver cirrhosis are more prone to acute liver dysfunction, which is more likely to cause bloodstream infections (Weber et al., 1984; Talley et al., 2016). Our reported case involves a patient with underlying cirrhosis and severe liver dysfunction, which shares similar high-risk factors for developing bloodstream infections to those reported in some previous cases. Most cases of peritonitis caused by P. multocida infection have been reported in the context of peritoneal dialysis (Cooke et al., 2004; Rondon-Berrios and Trevejo-Nunez, 2010), although a few cases of peritonitis without peritoneal dialysis have been reported (Vakil et al., 1985; Fernández-Esparrach et al., 1994). In our case, the patient had underlying cirrhosis but no kidney disease or history of peritoneal dialysis, which is uncommon. P. multocida colonizes the respiratory tract, and pneumonia, empyema, and lung abscess have been reported as manifestations in previous cases (Fernández-Esparrach et al., 1994; Lion et al., 1999; Kofteridis et al., 2009). In our case, the main manifestation was pneumonia, accompanied by a small amount of pleural effusion, but it did not progress to severe empyema or lung abscess. A similar case was previously reported involving a patient from a hospital in Barcelona, Spain, with underlying liver cirrhosis who was admitted due to P. multocida infection resulting in bloodstream infection, peritonitis, and empyema. This patient had no history of peritoneal dialysis but had a previous cat scratch and eventually developed progressive liver failure and died. In our case, the patient developed bloodstream infection, peritonitis, and pneumonia after P. multocida infection, despite no history of animal exposure. However, the patient had a favorable outcome after active treatment, highlighting the fact that P. multocida can cause multi-organ infections in immunocompromised patients. Without timely and aggressive treatment, these infections can lead to systemic organ dysfunction and even death.

The patient in this case had underlying cirrhosis, and the results of lymphocyte subpopulation analysis showed the total number of lymphocytes and the absolute number of CD4⁺ T cells and CD8⁺ T cells decreased significantly, indicating immunodeficiency. Previous studies have shown that P. multocida infections are often associated with T-cell-mediated immune damage (Hildebrand et al., 2015), and the decrease in T-lymphocyte subpopulation count and function may have contributed to the multi-site infection in the patient. Cytological examination of the ascitic fluid in this patient indicated peritonitis caused by P. multocida, although ascites cultures yielded negative results. This could be attributed to the early use of effective antibiotic therapy and the delayed ascites culture (performed on the third day of admission). In addition, conventional bacterial cultures may have lower sensitivity compared to next-generation sequencing in diagnosing bacterial infections in abdominal fluid (Goelz et al., 2021), especially when patients have received early antibiotic treatment, highlighting the limitations of standard bacterial cultures (Yoo et al., 2020).

Furthermore, the patient presented with a cough and slight chest tightness, and moist rales were detected upon auscultation of the lungs at admission. Pulmonary infection foci and pleural effusion were observed; however, owing to the minimal amount of pleural effusion, no thoracentesis or drainage was performed. Fortunately, with effective antimicrobial treatment, the pulmonary infiltrates and pleural effusion resolved, suggesting that the primary concern was pneumonia and pleural effusion caused by P. multocida infection. The drug sensitivity testing of P. multocida in this case revealed sensitivity to penicillin, cephalosporins, quinolones, and other commonly used antibiotics, which is consistent with previous case reports (Rondon-Berrios and Trevejo-Nunez, 2010; Abdelkarim et al., 2014; Katechakis et al., 2019; Hanson et al., 2022). Upon admission, ceftriaxone was chosen as the empirical antimicrobial treatment, and subsequent drug sensitivity testing confirmed its effectiveness. However, owing to the development of a rash in the patient, ceftriaxone allergy was considered, leading to a switch to levofloxacin for anti-infective therapy. In addition, performing ascites drainage while undergoing antibiotic therapy was a crucial measure for the success of treatment in this case.

In conclusion, we presented a case of a patient with liver cirrhosis who developed a multi-site infection with P. multocida, resulting in bloodstream infection, peritonitis, and pneumonia, despite no history of animal exposure. The patient received antimicrobial therapy with ceftriaxone followed by levofloxacin and underwent concurrent paracentesis drainage. Subsequently, his body temperature returned to normal, and both the ascites and pulmonary infiltrates resolved, resulting in a favorable prognosis. This case demonstrates that the use of effective antibiotics, along with local drainage intervention, is crucial for the successful treatment of patients with multi-site invasive infections caused by P. multocida.

The original contributions presented in the study are included in the article/supplementary material. Further inquiries can be directed to the corresponding author.

The studies involving humans were approved by the Ethics Committee of Affiliated Dongyang Hospital of Wenzhou Medical University. The studies were conducted in accordance with the local legislation and institutional requirements. The participants provided their written informed consent to participate in this study. Written informed consent was obtained from the individual(s) for the publication of any potentially identifiable images or data included in this article. Written informed consent was obtained from the participant/patient(s) for the publication of this case report.

BL: Data curation, Methodology, Writing – original draft, Writing – review & editing. XF: Investigation, Resources, Writing – original draft. TY: Methodology, Validation, Writing – original draft. KS: Resources, Visualization, Writing – original draft. SW: Formal Analysis, Resources, Writing – original draft. YS: Writing – original draft, Conceptualization, Funding acquisition. XP: Writing – original draft, Methodology, Software, Visualization, Writing – review & editing.