Salmonella typhimurium abscess of the chest wall

Background

Non-typhoid Salmonella (NTS) can cause not only self-limited acute gastrointestinal infections, but also bacteremia with or without extra-intestinal focal infections. Such complications usually develop in children, or in adults with predisposing conditions or underlying diseases that compromise host defenses. Here, we describe a case report of an unusual site of NTS infection in a patient with diabetes mellitus.

Case Report

A 73-year-old man was admitted to our hospital for left chest pain, diarrhea, and fever. His past medical history was remarkable for hypothyroidism, arterial hypertension, and insulin-dependent diabetes mellitus. Seven weeks before the hospital admission, the patient had gastroenteritis followed by left basal pneumonia with pleural effusion. At that time, he received a 2-week regimen of amoxicillin/clavulanate and seemed to be eventually cured.

At hospital admission, physical examination was unremarkable except for a pasty and floating swelling, 4 cm in diameter, on the left side of his fifth intercostal space. Blood examinations were normal except for neutrophil leucocytosis (white blood cells 16 560/mm3 – normal values 4000–10 000/mm3; neutrophils 13 910/mm3 – normal values 2000–7500/mm3) and elevation of C-reactive protein and erythrocyte sedimentation rate (ESR) (142.1 mg/L – normal value <5 mg/L – and 99 mm/h, respectively).

Chest X-ray showed a small left basal consolidation with little concomitant pleural effusion, while CT scan of the thoracic wall (Figure 1) showed an 8×5 cm abscess with sand-glass morphology near the last cartilaginous arch on the left, without signs of bone involvement. Percutaneous incision of the lesion revealed the abscess was extending into the endothoracic space through a perforation of the intercostal muscles. The culture from the drained pus was positive for Salmonella typhimurium, which was sensitive to fluoroquinolones and trimethoprim-sulfamethoxazole, but was resistant to ampicillin. Treatment with ciprofloxacin by intravenous route was given, with clinical improvement. After 20 days, culture of swab from the chest wall lesion was negative, the chest wall breach was surgically sealed, and antibiotic therapy switched to oral ciprofloxacin for a further 20 days because of the persistence of fever. At 2-month follow-up, the chest X-ray showed a nearly total resolution of the lesion and pleural effusion, and the patient was fully recovered, with no evidence of disease persistence or recurrence.

Discussion

NTS are gram-negative bacilli of the family of Enterobacteriaceae, which can be acquired from multiple animal reservoirs. Human transmission occurs by many routes, including consumption of food animal products, especially eggs, poultry, undercooked meat and dairy products, fresh produce contaminated with animal waste, contact with animals or their environment, and contaminated water [1]. Salmonellosis may present in different clinical forms, ranging from asymptomatic chronic carrier to gastroenteritis, bacteriemia, and extra-intestinal infections [1]. In recent years, several case series of NTS infection with extra-intestinal localizations have been reported in many countries (Table 1) [2–10]. Among the extra-intestinal localizations of NTS, blood stream infections are the most common, representing the 94.3% in a case series in the USA between 1996 and 2006 [2] and 82% in a Danish case series of 135 patients observed between 1991 and 1999 [3]. Other reported extra-intestinal localizations of NTS include: urinary tract infection, endovascular infection and endocarditis, meningitis, osteomyelitis, pneumonia, and soft-tissue and other visceral involvement. Pneumonia, with or without pleural empyema, and soft-tissue abscesses represent uncommon complication of NTS infection, accounting for 10% [4] and from 3.7% [3] to 7.3% [5], respectively, of extra-intestinal focal infections. To the best of our knowledge, chest wall abscesses caused by non-NTS have been reported only in 6 patients between 1990 and 2011: 4 of them had no underlying disease or predisposing condition [11–14] and 2 patients had AIDS [15,16]. Most extra-intestinal localizations of NTS infections develop in pediatric patients and in patients with underlying diseases or predisposing conditions, such as malignancies, diabetes mellitus, immunosuppressive therapies, liver cirrhosis, renal insufficiency, or HIV infection [4–9]. Indeed, our patient had diabetes mellitus.

Regarding the different Salmonella species isolated in systemic and extra-intestinal focal infections, S. enteritidis has been reported as the most common in the majority of the studies [5,7–9], followed by S. typhimurium and S. heidelberg, but the frequency of the different isolated Salmonella species varies geographically (Table 2).

Conclusions

Although NTS pleuropulmonary and soft-tissue involvements are quite uncommon, in our case we assume that S. typhimurium caused the gastroenteritis and, by blood stream spread, pneumonia and pleural effusion. Afterwards, the organism entered into the chest wall by contiguity. Alternatively, a non-Salmonella-induced pneumonia with resulting local inflammation might have facilitated a deposition of Salmonella in the nearby chest wall, finally leading to the abscess. Our case suggests that NTS should be considered as a possible cause of chest wall abscess in individuals with recent history of gastroenteritis complicated by pneumonia and pleural effusion.