Empyema Thoracis from Salmonella Choleraesuis

To the Editor: The clinical presentations of nontyphoidal Salmonella infection are protean, including gastroenteritis (most common), bacteremia, septic arthritis, osteomyelitis, and endovascular infection. (1). Despite the growing number of patients with invasive infection due to nontyphoid Salmonella, reports of thoracic empyema due to these organisms remain rare (2–6). We searched the computer database of our microbiology laboratory for patients with positive pleural effusion culture from June 1997 to February 2004. Patients were included if they met the following criteria: 1) thoracentesis recovered purulent pleural fluid; 2) microorganisms identified by microscopic examination; and 3) a Salmonella species isolated from a pleural effusion specimen. Isolates of Salmonella were identified to the serotype level, according to the Kauffman and White scheme, using somatic and flagellar antigens (Denka Seiken Co., Ltd., Tokyo, Japan) and also by conventional methods and the Phoenix System (panel type, NMIC/ID4) (Becton Dickson, Sparks, MD, USA) (7). Susceptibilities of Salmonella isolates to ampicillin, cefotaxime, chloramphenicol, ciprofloxacin, and trimethoprim-sulfamethoxazole were determined by the disk diffusion method. Organisms were categorized as susceptible or resistant to the antimicrobial agents tested on the basis of National Committee for Clinical Laboratory Standards (NCCLS) guidelines (8). Antimicrobial therapy was considered to be appropriate when the antimicrobial agent was active in vitro by the disk diffusion susceptibility method against a Salmonella isolate. During the study, 973 patients with a diagnosis of empyema thoracis were identified; 12 (1.23%) of these patients, including 9 men and 3 women, were infected with Salmonella species. The clinical characteristics of the 12 patients are summarized in the online Appendix Table (available from http://www.cdc.gov/ ncidod/eid/vol11no09/05-0030_ app.htm). The median age was 49 years; 1 patient was >65 years of age. Underlying diseases were present in all patients, including 7 with malignancy, 5 with gallstones, and 3 each with diabetes mellitus and chronic renal failure. Five patients had used antacids and 3 patients had received chemotherapy or steroids. Ten patients (83.3%) were immunocompromised and had a variety of illnesses, including malignancy, liver cirrhosis, and diabetes mellitus. Common symptoms were dyspnea (83.3%), fever (75%), and cough (50%). Analysis of pleural effusion showed a median leukocyte count of 25,600/μL, a lactate dehydrogenase level of 513 U/L, and a glucose level of 88 mg/dL. Gram staining was conducted on 3 patients’ pleural effusion but none of them showed positive results. Twenty-three Salmonella isolates were recovered as the sole pathogen from various clinical specimens, including pleural effusion (15 isolates), blood (6 isolates), ascites (1 isolate), and aortic wall (1 isolate). Among the 12 patients with empyema thoracis, 4 had Salmonella enterica serotype Typhimurium (S. Typhimurium) and 1 had group C2 Salmonella during 1997–1999; 7 patients had Salmonella enterica serotype Choleraesuis (S. Choleraesuis) after 1998. All S. Typhimurium and group C2 Salmonella were isolated from pleural effusion specimens, but S. Choleraesuis was isolated from multiple extrapulmonary sites including blood, ascites, and aortic wall (Online Table). Although the number of study cases is limited, it may suggest that S. Choleraesuis is more invasive than 2 other Salmonella species. Among the S. Choleraesuis isolates recovered from 7 patients, 2 were resistant to ampicillin and sulfamethoxazole-trimethoprim, 3 were resistant to chloramphenicol, 1 was resistant to ciprofloxacin, and all were susceptible to cefotaxime. All S. Typhimurium isolates were susceptible to sulfamethoxazole-trimethoprim, ciprofloxacin, and cefotaxime. Two of the 4 patients had isolates that were resistant to chloramphenicol, and 2 other patients had isolates that were resistant to ampicillin. The group C2 salmonella isolate was resistant to chloramphenicol only. Among the 12 Salmonella isolates from patients with empyema thoracis, 9 were resistant to >1 commonly used antimicrobial. Treatment and outcome information was available for 11 of the 12 patients. All 11 patients received antimicrobials drugs (median duration 35 days); this therapy was appropriate in 9 of 11 patients. Six patients had thoracentesis, 2 had close tube thoracostomy, and 1 had open drainage. One of the 4 patients with S. Typhimurium empyema who did not receive appropriate antimicrobial drugs died. In contrast, 4 (57%) of the 7 patients with S. Choleraesuis infection, including 1 who did not receive appropriate antimicrobial therapy, died. Another factor related to outcome was drainage. One (20%) of the 5 patients who underwent tube thoracostomy or thoracoscopy died, while 3 (50%) of the 6 patients who underwent thoracentesis died. All 3 of these patients had S. Choleraesuis. Most (92%) of our patients were <65 years of age. These data indicate that Salmonella should be considered as a potential cause of thoracic empyema, even in younger patients, especially in the presence of malignancy or hepatobiliary disease. More than half of our patients had used antacids or had suffered from gallstones. This finding suggests that susceptibility to