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Clinical Infection & Immunity

Case Report

Volume 1, Number 1, September 2016, pages 27-28

Invasive Non-Typhoidal Salmonella in an Immunocompetent Host

Most cases of salmonella are foodborne and recent outbreaks have been linked to the ingestion of eggs, cheese, fresh vegetables and poultry [1]. Approximately 5% of individuals with salmonella gastroenteritis will develop bacteremia [2]. Invasive non-typhoidal salmonella (iNTS) infections are becoming more prevalent worldwide, particularly in Africa and Asia where they are a significant cause of mortality [3]. We describe a case of iNTS which is extremely rare in patients without underlying immunodeficiency or predisposing condition.

A previously healthy, immunocompetent 38-year-old man presented with 5 days of subjective fevers and chills. Approximately 1 week preceding the fevers, the patient experienced 5 days of watery, non-bloody diarrhea that resolved spontaneously. The patient also complained of generalized weakness, malaise and dry cough. He denied nausea or vomiting, chest pain, shortness of breath or abdominal pain. The patient admitted to ingestion of turkey burgers which may not have been well cooked. The patient’s friend also experienced similar symptoms including diarrhea, fatigue and fevers which resolved after a few days. The patient was employed as a coast guard. He denied exposure to pets or recent travel. He did not smoke, drink alcohol or use illicit drugs. He reported having multiple female sexual partners. Soon after the start of the symptoms, the patient visited his primary care physician who recommended oral hydration and rest. However, he continued to have persistent fevers, night sweats and weakness which prompted him to seek care in the emergency department.

The patient’s initial vital signs were as follows: pulse 83 beats/min, blood pressure 138/87 mm Hg, temperature 100.8 °F and respiratory rate 18/min. On physical exam, no skin rash was noted, lungs were clear to auscultation, heart sounds were normal with no rubs, murmurs or gallops and abdomen was soft, non-tender, and non-distended.

The patient was admitted to the medical floor. Blood cultures were drawn and a CT scan of the abdomen was obtained. The patient was started on meropenem and metronidazole. Blood cultures were found to be positive for Gram negative rods and the antibiotic regimen was changed to ceftriaxone. CT scan of the chest, right upper quadrant ultrasound and transthoracic echocardiogram were unremarkable. A CT scan of the abdomen revealed mildly enlarged right lower quadrant mesenteric lymph nodes. Two sets of blood cultures were positive for salmonella species, group B sensitive to ampicillin, ciprofloxacin, sulfamethoxazole/trimethoprim and ceftriaxone. Feces culture was negative for growth. HIV Ag/Ab test was negative. The patient continued to spike fevers with a Tmax of 103 °F despite 4 days of treatment with ceftriaxone. He was then switched to ampicillin for the remaining 4 days of hospitalization. The patient remained febrile until the last 2 days of hospitalization and was discharged on a course of ciprofloxacin for 14 days.

NTSs including Salmonella enteridis, Salmonella typhimurium and Salmonella newport are a prevalent cause of gastroenteritis worldwide [4]. Invasive salmonellosis is rarely seen in immunocompetent hosts but the overall incidence is becoming an important emerging cause of invasive infections worldwide [5]. In North America, there are 1,716,000 cases per year and 2,800 deaths from non-typhoidal salmonella gastroenteritis [6]. Worldwide, Kenya and Malawi had the highest disease burden globally [3]. This infection can occur across all age ranges but mostly presents in a bimodal distribution: < 5 years old and 30 - 35 years old [3, 7]. Patients who are infected with invasive salmonella are also typically co- infected with HIV or malaria [8]. A recent analysis in Finland, Denmark, and Australia revealed that within different regions of each country, there were different isolates of salmonella [5].

Salmonella is spread primarily through oral transmission with an incubation period between 6 and 72 h [2]. In high-income countries, NTS typically results in a self-limiting diarrheal illness, with a small proportion developing bacteremia and extraintestinal focal infections. It has been reported to cause musculoskeletal, central nervous system, pulmonary, cardiovascular and urinary infections [4].

Invasive disease can have serious end organ damage including pericardial seeding resulting in cardiac tamponade and ventricular wall rupture [9], endocarditis, and arthritis [10]. Salmonella bacteremia is treated with monotherapy for 10 - 14 days. Salmonella responds well to fluoroquinolones and third-generation cephalosporins which are the preferred drug classes in the United States. However, there are reports of emerging resistance to the fluoroquinolones worldwide [10]. In developing countries, azithromycin is the preferred empirical treatment and can be combined with ceftriaxone for life-threatening situations. Surgical treatment is indicated if endocarditis or infectious arteritis is documented and antimicrobial therapy is extended to 6 weeks after surgery. Ceftriaxone remains the drug of choice for central nervous system involvement [2]. As salmonella is primarily transmitted orally, reducing the spread of the bacteria requires proper hygiene with emphasis on handwashing and proper preparation of food [11].

We described here an extremely rare case of a healthy, immunocompetent male patient who developed iNTS with hematogenous spread.

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